Stpm Physics Kedah 2007 P2

2007 Kedah Physics Paper 2 Section A [40 marks]

3 The diagram below shows the face and interface temperature of a composite slab consisting of four materials: P, Q, R and S of different thickness through which the heat transfer is steady.

1 The diagram below shows a pulley system consisting of two pulleys of weight 10 N each. The system is doing work to lift a load of 100 N upwards for 10 m at constant speed.

List the materials from the lowest thermal conductivity to the highest thermal conductivity. Explain clearly how you arrive at your answer. [4 marks]

Calculate (a) the total work done by the pulley system. [2 marks] (b) the magnitude of the force F, (c) the efficiency of the system. 2 y = 4 sin 3t cos 4x is an equation of a standing wave. Find (a) the amplitude of a point P at x = 1.5 m, (b) distance between two successive nodes,

4 The Earth has an outer layer (thin compared to its radius) which has thermal conductivity of about 2.0 W m–1 K–1. On the average, the temperature on the surface of the Earth increases by about 30 °C for every kilometre below it. Estimate the rate of heat loss through the surface of the Earth. (Radius of Earth is 6.0 x 106 rn) [5 marks]

5 The diagram shows a spring with spring constant [2 marks] k hanging on a ceiling. The other end of the spring is hung a rectangular coil ABCD of n turns. Length of [1 mark] side CD is l. Magnetic field intensity B is acting into the bottom region of the coil. If l is the flow of current in the coil, in terms of n, I, B, l and k, determine the difference in the distance moved by the coil when the direction of the [1 mark] current is reversed. [5 marks] [3 marks]

(c) frequency of oscillation of each particle in the wave. [2 marks]

6 A milliammeter has a resistance of 40 Ω and a full-scale deflection of 20 mA. Section B What is the value of resistance R that has to be connected in series with the [60 marks] milliammeter so that it can measure a maximum voltage of 5.0 V? [5 marks] 9 (a) Explain what is meant by angular velocity ω and angular momentum L of a particle which is rotating about a point 0. 7 The figure below shows diagrammatically the various energy levels in the [2 marks] hydrogen atom. (b) If the mass of the particle in (a) is m and the radius of rotation of the particle is r, show that the kinetic energy can be expressed as

L2 . 2mr 2

[4 marks] (c) (i) Write down an expression for the gravitational attractive force F on an object in a gravitational field of a planet. [2 marks] (ii) Write down an expression for the gravitational field strength g which acts on the object at this distance. [1 mark] (d) The figure below shows a 1 kg object placed on the surface of the earth. The sphere X is a concentric sphere of the Earth with radius 4000 km and density 2800 kg m–3.

(a) What is the wavelength of a photon that will ionize a hydrogen atom in the ground state and give the ejected electron a kinetic energy of 3.4 eV? [3 marks] (b) A neutron with a kinetic energy of 3.4 eV collides with a stationary hydrogen atom in its ground state. Explain why the collision must be elastic. [2 marks] 8

(a) What is meant by the binding energy of a nucleus?

(b) The binding energy per nucleon of nucleus in atomic mass unit ?

16 8

[1 mark] O is 7.98 MeV. What is the mass of the

If the radius of Earth is 6400 km, calculate (i) the gravitational attractive force on the kg object by sphere X [2 marks] (ii) the gravitational field strength of sphere X on the 1 kg object

[2 marks] (iii) the difference in gravitational field strength of sphere X on the 1 kg [4 marks] object to the gravitational field strength of the Earth. [2 marks]

10 (a) Define stress, strain and Young’s Modulus.

11 (a) The diagram below shows a 50-tum, 10 cm long solenoid with a 10-turn inner [3 marks] coil lying along its axis. The inner coil, which has a cross-sectional area of 1.0 cm and (b) The graph below shows variation of force with extension for a wire A. The a resistance of 0.010 Ω, is connected to a galvanometer. The solenoid, which has a wire obeys Hooke’s law over the range of extensions considered. total resistance of 1.0 Ω is connected to a battery that steadily decreases in voltage from 12 V to 0 V in 0.50 s. then remains at 0 V for t > 0.50 s. (i) As the voltage of the solenoid begins to decrease, determine the direction of current (left to right or right to left) that flows through the galvanometer. Explain your answer. [2 marks] (ii) Find the maximum and minimum magnetic flux density along the axis of the solenoid. [3 marks] (iii) Draw a graph to show the current in the inner coil as a function of time for 0 ≤ t ≤ 1.0 s. Include a numerical scale on the vertical axis. [4 marks] (b) The graph below shows the variation of voltage, V against time, t for an electric source. (i) If the wire has a diameter of 0.40 mm and its unstretched length is 2.0 m, calculate the Young's modulus of the steel. [3 marks] (ii) A second wire B is made of the same steel. It has the same unstretched length as A, but twice the diameter. Draw accurately on a copy of the above figure the force-extension graph for this wire. Label your graph B. [3 marks] (c) As shown in the graph below, if a stress-strain curve is plotted for the loading and unloading of a piece of rubber, the two parts do not coincide, where OABC is for stretching and CDEO for contracting. (i) What does the area enclosed by OABC and the strain axis represent? [2 marks] (ii) What does the area enclosed by CDEO and the strain axis represent? [2 marks] (iii) The shaded area is called a hysteresis loop. What does the hysteresis loop represent? [2 marks]

Determine the (i) frequency, (ii) root-mean-square value of the voltage for the source. The source is connected to a 20 mH pure inductor. Find the (iii) reactance pf the circuit,

[2 marks]

[1 mark] (iv) root-mean-square value of the current flowing through the circuit. [1 mark] (v) Draw graphs on the same axis to show the phase relationship between the current, I and voltage, V through the inductor. [2 marks]

12 (a) What Is the focal length of a mirror?

[1 mark] 14 (a) (i) Energy is released from nuclear fission and nuclear fusion. Explain what is meant by nuclear fission and nuclear fusion (b) An object is placed 6.0 cm in front of a concave mirror that has a 10.0 cm [2 marks] focal length. (ii) State two differences, from the energy viewpoint, between nuclear fission (i) Determine the location of the image and draw a ray diagram to illustrate and nuclear fusion. your answer. [5 marks] [2 marks] (ii) The object is 1.2 cm high. Find the height of the image and state the characteristics of the image formed. [4 marks] (b) Sketch a graph showing how the binding energy per nucleon varies with nucleon number and show how both nuclear fission and nuclear fusion can be (c) Rear-view mirrors in newer cars often have a warning label that reads explained from the shape of this graph. ‘OBJECTS IN MIRROR ARE CLOSER THAN THEY APPEAR'. What type of rear[5 marks] view mirrors are they? Explain your answer. [3 marks] (c) A fusion reaction is represented by the equation below. 2 3 4 1 (d) Suppose you would like to start a fire in the wilderness. Which type of mirror 1 H + 1 H → 2 He + 0 n would work best? Explain your answer. [2 marks] 13 (a) From the characteristics of radiation emission, differentiate between wave theory and quantum theory for radiation. [2 marks] (b) The Einstein photoelectric effect equation is given as follows:

1 2 mv + W 2 1 2 (i) State the meaning of the terms hf , mv and W in the formula above. 2 hf =

Mass of deuterium Mass of tritium Mass of helium Mass of neutron

2 1 3 1 4 2 1 0

H H He n

= 2.014102 u = 3.016049 u = 4.002603 u = 1.008665 u

(i) Calculate the energy, in MeV. released from this fusion reaction.

[4 marks] (ii) Calculate the energy released from fusion of 10.0 g of the hydrogen nuclei [3 marks] involved. (ii) With the aid of an equation involving the term W, state the condition for [2 marks] the frequency of radiation so that photoelectric emission can occur. [1 mark] (iii) Explain why photoelectrons released have different velocities even though incident radiation of fixed frequency is used. [1 mark] (c) In a photoelectric effect experiment, the stopping potentials corresponding to incident radiation of wavelengths 300 nm and 400 nm are 1.8 V and 0.8 V respectively. (i) Explain what is meant by stopping potential, and hence, calculate the maximum velocity of the electrons emitted by an incident radiation of wavelength 300 nm. [3 marks] (ii) Estimate the value for Planck’s constant from the given information above. [3 marks] (iii) Sketch a graph of potential difference against frequency and subsequently show the way to determine the Planck constant. [2 marks]